[Solved] Why does this ARM assembly loop cause an infinite loop?MOV R4, #2 loop: ADD R4, R4, #1 BNE loop — Ans: SUBS instruction missing to update flags | ARM Architecture

ARM Architecture - Control Flow Instructions

Why does this ARM assembly loop cause an infinite loop?

MOV R4, #2
loop:
ADD R4, R4, #1
BNE loop

ASUBS instruction missing to update flags

BMOV instruction is incorrect

CLabel syntax is wrong

DADD instruction should be SUB

Step-by-Step Solution

Solution:

Step 1: Understand flag updates for branching
BNE depends on condition flags set by instructions like SUBS.
Step 2: Identify missing flag update
ADD does not update flags here, so BNE always branches causing infinite loop.
Final Answer:
SUBS instruction missing to update flags -> Option A
Quick Check:
Branch needs flag update instruction [OK]

Quick Trick: Use SUBS to update flags for BNE to work [OK]

Common Mistakes:

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